With Hand Pollination You must pollinate during the short time between blooming and bud drop, and you must pollinate each flower cluster individually.

An alternative to hand pollination is pollinating spray, sometimes called blossom set spray. Pollination sprays contain cytokinins, which are hormones that trigger the growth of the tomato ovary. In commercial greenhouses, workers spray the pollination spray on newly opened tomato blossoms until the spray runs off. Doing so does not pollinate the tomato despite the fact that these sprays are typically called pollination spray. Saturating the ovary of the tomato with cytokinins causes it to grow into a tomato without pollination. Fruit from these artificially stimulated tomatoes tends to be larger and more abundant than naturally pollinated tomatoes.

Bumblebees

You can also use a pollination method that is less labor-intensive than either hand pollination or spraying plants with pollinating spray -- using bumblebees. Various companies supply bees. Once installed in a hive inside the greenhouse, the bees fly from plant to plant, looking for nectar and pollen to eat. They land upside down on the flower and bite into the staminal tube. Their wing muscles vibrate as they hang from the blossom. This vibration causes enough movement to shake the pollen onto the stigma and pollinate the tomato.